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balloon_nodes:ah3

AH3

Aim

  • Third UKHASnet test flight
  • Based on data from previous flight it appears that temperature has a significant impact on the performance of the node at altitude. The flight of AH3 is to attempt to stabilise the radio's temperature and therefore maintain the nodes frequency and data rate.

Components

  • AH3
    • Moteino R4 with RFM69HW
    • Mosfet/Resistor heater positioned over the radio crystal
    • 3x AA lithium batteries

Flight

Easy launch due to good weather, due to high speed jetstream we had the option of either a quick flight with certain landing in the North Sea or a European floater. We elected the quick flight to allow for the longest period of time within range of ground nodes. The payload was launched under an 800g Pawn balloon with an additional old 434 RTTY tracker 'X0'. While the node performed on the ground it very quickly lost contact with the ground nodes on launch. Packets were received for a few minutes and then stopped coming through. Packets were then received by DB02 and DB03 as the payload passed over. Overall the range was very poor with the node reporting that it had only received one packet. At the launch site we investigated the poor performance and found that our ground nodes were regularly freezing up (and so may have missed packets). Looking on a funcube dongle showed a significant interference.

The suspicion is that the noise is triggering the rx function within the receiver and this is locking up. If the ground stations are getting caught by local interference there is a high chance that an airborne node will be in the same situation.

To test the situation further we went on to launch a second node (BALL1) under a 100g Totex balloon. This showed a very similar pattern of quickly going out of range and then as it passed over the DB02/DB03 network passing some packets through and then disappearing. Unfortunately there were no balloon to balloon communications.

Data for AH3

Temperature Voltage RSSI 1 RSSI 2

The graph below shows the RSSI from the DB02 node, it is possible to identify both AH3 and BALL1 passing over this node and communicating with it.

Outcomes

  • The current routing allows for seamless merging of networks, AH3 flew over DB02/DB03 and was able to downlink through it.
  • The range is very limited (~30km max)
  • The RFM69HW is struggling with local interference and getting locked up

Potential Solutions

  • Move the networks frequency to avoid widespread interference
  • Adjust the settings to improve the performance and efficency
  • Internally reset the radio module to avoid it locking up.
balloon_nodes/ah3.txt · Last modified: 2014/11/02 19:56 by jcoxon